The present invention is directed to a dental handpiece comprising a drive section or part, which has a drive shaft extending from a drive motor, a handle section, which is mounted for rotation on the drive section and contains a drive train for transferring rotation of the drive shaft to a rotatable acceptance socket for receiving a tooth treatment instrument such as a drill. The dental handpiece has cooling medium lines comprising line segments incorporated in each of the drive and the handle sections which line segments are interconnected by a coupling formed by a ring channel in one of the handpiece sections and a radial opening communicating the ring channel being provided in the other of the handpiece sections.
Dental handpieces, in which a cooling line is guided in the various handpiece sections, are recently enjoying an ever increasing use and such a handpiece is described for example in U.S. Pat. No. 4,007,529, which was based on German O.S. No. 24 31 472. In such a handpiece, problems have occurred with being able to readily clean or exchange the cooling lines which have a relatively small cross section and therefore are easily clogged.
In German O.S. No. 2,653,588, an attempt to solve this problem for the handle-side handpiece section was suggested. Such a solution is that an externally accessible closing or sealing member is provided on the outer jacket of the handle section. The closing or sealing member covers the location at which a transition is provided from a rectilinear, axial parallel proceeding segment or section of the cooling line to the radial section which extends to the ring channel. This closing or sealing member can be removed in case of a possible clogging of the segment. In the case of such a construction, several disadvantages occur. For example, in addition to O-ring seals on the sealing member, which are necessary for the rotation of the two handpiece sections, additional sealing locations are created. Moreover, the proposed solution does not solve the problem of providing easy cleaning and/or exchanging of possibly clogged lines or conduits directly at the rotary coupling location. For example, in the region of the transfer of the agent from the drive section to the handle section and specifically in the region of the drive section itself, the solution does not provide an easy cleaning and/or exchanging of clogged lines.